In recent years, balloon catheters have been used for improving lesion affected areas (stenosed parts) in body lumens. A balloon catheter normally includes an elongate shaft portion, and a balloon which is provided on the distal side of the shaft portion and is inflatable in the radial direction. After the balloon in a deflated state is brought to a target site in the body by way of a small body lumen, the balloon is inflated, whereby the lesion affected area can be pushed wide open.
If a lesion affected area is forcibly pushed wide open, however, excessive proliferation of smooth muscle cells may occur, causing new stenosis (restenosis). In view of this, recently, drug eluting balloons (DEBs) wherein an outer surface of a balloon is coated with a drug for restraining stenosis have been used. The drug eluting balloon, by being inflated, is able to instantaneously release the drug contained in the coating on the outer surface of the balloon to the lesion affected area and transfer the drug to the living body tissue, thereby restraining restenosis.
In recent years, it has been becoming clear that the morphological form of the drug in the coating on the balloon surface influences the releasing property of the drug from the balloon surface and/or the transferability of the drug to the tissue at the lesion affected area. For this reason, it is said that it is important to control the crystalline form or amorphous form of the drug.
A variety of methods have been proposed for coating a balloon with a drug. For instance, U.S. Pat. No. 8,597,720 discloses a method in which a coating solution containing a drug (therapeutic agent) is supplied to a surface of a balloon while the balloon is being rotated, and the coating liquid is dried to form a coating layer containing the drug.